Process of preparing fuels for use



Sept. 6, 1932. RlCHARDSCN 1,876,168

PROCESS OF PREPARING FUELS FOR USE Filed Aug. 18. 1928 3 Sheets-Sheet 1 Sept. 6, 1932. E. A. RICHARDSON PROCESS OF PREPARING FUELS FOR USE Filed Aug. 18, 1928 3 Sheets-Sheet 2 gvwwtoz W M MM 35 elf tom pt 932- E. A. RICHARDSON 1,876,168

PROCESS OF PREPARING FUELS FOR USE Filed Aug. 18, 1928 3 Sheets-Sheet 5 UNITED STATES PATENT OFFICE EDWARD RICHARDSON, OF BETHLEHEM, PENNSYLVANIA I'IBOGESS OF PREPARING FUELS FOR USE Application filed August 18, 1928. Serial No. 300,569.

My invention relates to a process of gasifying fuels for use in burners, stoves, furnaces, kilns, metallurgical processes, internal combustion engines, etc.

The object of my invention is to provide a process of gasifying fuels so as to prepare liquid fuels for use in an advantageous manner, my process being such as to permit suitable latitude in operating-pressures and temperatures, according to the different liquid fuels treated and the uses to which they are to be applied.

My invention involves the treatment of a liquid fuel in such a manner as to supply the same for use, as when about to be burned or oxidized, at temperatures and preferably to mixed fuels which may be used in accordance with my invention, as, for example, hydrocarbon fuels, such, for instance, as petroleum fuels, examples of which would be kerosene, gasolene, distillate, fuel oils, also mixtures, as, for instance, 'mixtures containing benzol, or mixtures, containing alcohol, etc. The fuel, when prepared in accordance with my invention, does not require atomization, as in the case of a fuel supplied in the form of a liquid, inasmuch as by supplying fuel in the neighborhood of the critical temperature and pressufi thereof the cohesive forces between the particles have been overcome to such an extent that they will act like a gas and mix with the air or other oxidizing agent very thoroughly and rapidly so that combustion will be assisted to the fullest possible extent. Also, the fuel prepared in accordance with my invention, by reason of the pressure at which it is supplied for combustion purposes, will overcome any resistance or pressure necessary tov be dealt with in the proper and adequate supply of the fuel for the particular use. Furthermore, the temperature of the fuel is sufiiciently high to materially accelerate the rate of combustion or metallurgical reduction in the process in which it is used. An important advantage, furthermore, is that the final temperature after cooling by expansion, as in the apparatus or process in which the gaseous fuel is used, may be controlled in considerable measure by heating to higher temperatures than otherwise necessary before such expansion. Also, the cooling of the charge in an engine, as of the Diesel type, produced by the expansion of the injection air used to atomize the oil, may be done away with and the desired final temperature of the injected fuel may be made quite high, approaching the point of autoignition of the fuel, by controlling the temperature of the gaseous fuel be fore injection into theengine. Again, the supplying of the fuel in this manner in the uniform operation of the combustion apparatus or other installation, any sudden changes in volume which would occur through the boiling of a liquid fuel are avoided.

In general, my invention is carried out by subjecting the liquid fuel to a temperature and pressure in the neighborhood of the critical temperature and pressure thereof, although either the temperature or pressure or both may be much higher than the critical temperature and pressure according to the requirements of successful operation of the particular fuel-consuming devices, but not so high as to produce thermal decomposition of the fuel, in case this will interfere with the satisfactory operation of the fuel consuming devices. Higher temperatures, for example, may be used with higher pressures, these pressures, when decomposition does tend to take place, resulting in the production of denser molecules than at lower pressures with the same temperature, with the result that less carbon is thrown down than would otherwise be the case. However, in general, a longer time is necessary for such reactions to occur than the time factors in my process. This decomposition in known in the oil refining industry as cracking. It is well known, however, that where cracking of the oil occurs in the form of a liquid, there is a greater production of liquid products and a smaller deposition of carbon than when the fuel is treated in the form of a vapor. In accordance with my invention it is not one of the objects to produce cracked fuels and any cracking, therefore, which occurs is purely incidental and not essential.

By the critical temperature and pressure herein referred to I mean the critical temperature and pressure in the significance in which these terms are ordinarily used with regard to different liquids. In other words, for each liquid there is a temperature and pressure at which the volume of the vapor which can be formed from the liquid is no greater than the volume of the liquid itself. This is the critical point to which I mean to refer, that is to say, the temperature and the least pressure suflicient to prevent the boiling of the liquid. In accordance with-my invention it is generally desirable, and sometimes necessary, to use higher pressures than the critical pressure as the change in volume, in passing through the critical stage, is rather large. Also, in the case of fuels which are generally mixtures of liquid chemical compounds, there are, at times, other possible pointsof equilibrium between the liquid and vapor phases called plait points, due to the difference in composition of the vapor and the liquid, distinguished by the fact that an increase in the pressure of the vapor at such a point might produce a condensation of the liquid, which liquid, if the pressure is further increased, may be evaporated. In accordance with my invention I am particularly. interested in producing a gas by a process in which the volume increases with the temperature without boiling and without physical change in going from the liquid to the vapor state, the pressure being sufliciently great under normal conditions to prevent any sudden or very rapid changes in volume with the temperature.

The critical temperatures, pressures and volumes for many difierent pure or nearly pure compounds are known and are available in the works of Landolt-Biirnstein and the Physical Tables of the Smithsonian Institute, etc. In carrying out my invention, in case I use kerosene, for instance, as a fuel I may begin by assuming that the kerosene is pure octane, the critical pressure of which is 350 lbs. gage and the critical temperature about 570 F. In using a hypothetical fuel inaccordance with my process, the fuel would be run up to a pressure of 400 lbs. per square inch and the temperature to 700 F. or higher,

= expanding the fuel in a jet burner or similar device. Such a large amount of expansion takes place in the burner as to promote effective mixing with the air and causing the air to be drawn into the furnace in an effective manner. There would be no danger of cracking the oil as a temperature of at least 800 F. must be reached before any cracking begins. In case such fuel were used in an injection type oil engine having a maximum compression pressure of about 450 lbs. per

square inch, the fuel would have to be run up to as high as 900 lbs. to secure satisfactory operation of the fuel valves and sufiiciently rapid injection of the fuel. The temperature would be raised, accordingly, to insure the gas remaining dry after expansion to the 450 lbs. in the engine. Thus, if I should find it disadvantageous to allow condensation on expansion, my process permits me to avoid such condensation by raising the temperature of the gaseous fuel to an amount sufficient to insure dry gas after expansion. In the case of the kerosene we have been considering, a temperature of 700 F. is sufiicient, as the temperature after expansion would still be above 570 F., which is the critical temperature.

Where using mixed fuels of varying composition, such as fuel oils, a temperature of between 850 and 1100 F. and pressure of 180 to 225 lbs. per square inch would be used by reason of the differing compositions of such fuels sold under the same general specifications. In the case of such mixed fuels I have found it possible to determine the temperature and pressure needed in the following way, although I have found that in the actual operation of my invention the desired temperatures and pressures which are the most satisfactory for the purposes re quired may be determined in connection with the actual tests as hereinafter described, and through actual tests on and adjustments of the apparatus when applied to the apparatus or process with which the gaseous fuel is to be used. The approximate critical temperatures and pressure may be determined in the following manner:

First, estimate the proportion by weight of the different components. Second, determine or write down the chemical formulas for the components present, and the molecular weight of each compound. Thirdly, taking the pounds per thousand pounds of fuel of each, divide by the molecular weight of the component. The resulting figure is the number of mols of the compound in 1,000 lbs. bf fuel. Fourth, find the total number of mols of all components in the 1,000 lbs. of fuel by adding the mols of each component. Fifth, find the percentage which the mols of each component bear to this total.

The critical temperature of the mixture may be approximated by taking the absolute critical temperature of each component and multiplying it by the mol fraction for that component, adding all these partial temperatures for the absolute critical temperature of the mixture. Gases may be added to the fuels, if desired, and the properties of the resulting mixtures estimated on the same basis.

For determining the critical pressure, I proceed as follows: It is sufficient for most purposes to take the absolute critical pressure of each component, multiply by the mol fraction of that component, and add all the partial pressures for the critical pressure of the mixture.

Another method of procedure which I shall not describe in detail is to determine the a l and b coeflicients in Van der Waals equation for each component, wh ch equa-tlon 1s and find by similar steps the values of a and b for the mixture. From the equations which may be found in any theoretical physics, the critical pressure and temperature may be calculated from'these average coefficients. Other works on theoretical physics are available, which will give accurate methods for calculating the properties of mixtures, of which Van der Waals Continuitat des gasformigen und fiiissigen Zustandes is probably the best. The calculation of the exact values of a and b by theoretical methods is in general impossible. however, owing to lack of data on some of the constants involved.

The method of experimental determination of the critical point according to the definition requires filling partially several sealed glass containers of known volume with various quantities of the liquid mixture. The temperature is slowly raised. Those with too little liquid will boil as the temperature is raised. If the quantities are properly chosen, one or more of them will, as the critical temperature is reached, show a cloudy appearance throughout the whole tube when the critical point is reached, followed, at a slight increase in temperature, by an appearance of nothing but gas. Or, as the heated vapor is cooled, it can be subjected at given temperatures to high pressure until a temperature is reached at which a cloudiness appears. The range of temperatures in which cloudiness accompanies the application of pressure, may be quite large in thecase of mixtures. A certain low temperature will eventually be reached at which there will I be no cloudiness, but below which the liquid will appear on continued reduction of volume. The true critical point may well be defined as the point on the isothermal curve at which the slope is zero when the coordinates are pressure against volume, the isothermal used being that of highest temperature which will give such a slope.

In the case of pure ethyl alcohol, for example, its critical temperature is 517 K. (degrees kelvin or centigrade absolute) and its critical pressure 922 pounds per square inch. Its mol weight is 90. Water has a critical temperature of 647 K. and its critical pressure is 3,196 lbs. per square inch. The approximate critical points of ethyl alcohol containing 90% by weight of alcohol and 10% by weight of water, therefore, could be determined in the following way. The mol weight of water is 18. There are 900 lbs. of alcohol, or 10 mols in the mixture, and 100 lbs. of water or 5.56 mols. The mol fraction of water is .322, that of alcohol .678. I

should expect .678 X 517 plus .322 X 647 559 which may run up to 620 F. and 1200 lbs. per

square inch for certain purposes.

I can, also, at least roughly, plan my apparatus with a reasonable knowledge of the heat quantities, pressures, temperatures, jet

energies, volumes, and the like for quite a I range of cases which may arise in practice.

For instance, ample pumping capacity must be provided in any given gasifying process to permit of reaching any reasonable pressure in the neighborhood of the critical pressure which may be ex ected in using the fuels which may be gasi ed in the process. The heating surface required in the preheat'er will also vary considerably with the degree to which the fuel is heated above the critical point. I have made up a chart for estimating roughly the properties of gases in the neighborhood of or above the critical point. The pressures are given as fractions of the critical pressure, the temperatures as fractions of the critical temperature, and the volumes as fractions of the critical volume.

ing 1,000 1bs. by the number of mols in the mixture which for alcohol is 10 alcohol+ 5.5 H O=15.5. For the case of alcohol above, it amounts to 64.3 lbs. Hence all quantities apply to 64.3 lbs. of commercial, alcohol. The heat required, for instance, to raise the alcohol at constant pressure from .800 of the critical temperature in degrees absolute (975 F. absolute) or 320 F. to 1850 lbs. per square inch (1.12 times the critical pressure) and 610 F. (1.10 times the critical temperature) is 10,800 B. t. u. per mol at critical temperature 1,000 F. absolute which reduces to 10,500 B. t. u. for the given critical temperature and one mol, or to 164 B. T. U. per lb. To this must be added the heat to raise the alcohol from 60 F. to 320 F., or not less than 180 B. t. u. more (specific heat assumed at .7) If any appreciable chemical dissociation should occur, these fig- All quantities apply to one equivalent mol of mixture. This number is obtained by dividl of the gas.

ures would have to be increased. If the gas were expanded down to the critical temperature, I follow the constant entropy line 10.00 down to the isothermal curve 1.00. As there is nearly 500 B. t. u. difierence in heat capacity, or roughly 7.6 B. t. u. per 1b., this amount of kinetic energy may be developed in an expansion nozzle. This provides quite a satisfactory amount of energy for inducting the necessary air for combustion in a burner, or for agitating the contents of an engine cylinder for producing more rapid mixing and combustion. The temperature of the expanded gas is still much higher than the particles atomized by air or steam, so that there will be less delay in starting combustion.

The density of 90% alcohol at about F. is roughly .827. The critical density is roughly ,The density at 610 F and 1850 lbs. per square inch pressure is 333/235 or .142. The density after expansion is 333/307 or .109. The volumes per mol are roughly 1.21 cubic feet, 3.00 cubic feet, 7.05 cubic feet, 9.21 cubic feet for the different states above. Divide by 64.3 (mol weight) for the volumes per lb.

I shall next consider the amount of heat which can be transmitted to fluids under the pressures I anticipate, so that I may proportion the heating surface required in the heater 'with some degree of certainty. I find that the flow of heat between a gas and a metal surface is proportional to the specific heat of the gas, to the mean difference of temperature between the gas and the metal, and is a. function of the ratio of weight of gas flowing to the free area through the tube, pipe coils, or the like, the function, according to Reynolds law, being of the form where A and B are constant, or nearly so, for a given fluid, w is the weight rate of flow of the fluid, and a is the free cross section area through the tube bank or tube s. B is roughly proportional to the specific heat The same law holds for water and presumably for all fluids. Hence keeping these facts in mind, I may use such data as may be available on heat flow (Heat Transmission by Radiation, Conduction, and Convection, by R. Royds, edition of 1921, published in London by Constable and Company, Ltd, being a suitable authority), making use of the known or approximate value of the specific heat of the fuel as it flows through the heater, and design the heater on that basis.

While my invention is capable of being carried out in many different ways, I have shown only one type of apparatus for use in connection therewith in the accompanying drawings, in which Fig. 1 is a diagrammatic elevation, partly in section, of an apparatus which will be used in accordance with my invention;

Fig. 2 is a set of curves useful for approximating the desired pressures and temperatures used in my process, the amount of heat required, the energy available on adiabatic expansion, and the final pressures, volumes and temperatures after such expansions, information of value in adapting the process to its particular application, such curves to be used, only when more exact data on the thermal properties of the fuels used is lacking.

Fig. 3 is a diagrammatic side elevation of the apparatus shown as connected to the boiler of a power plant;

Fig. 4 is a partial cross section of the heater tubes on line AA showing the method of securing the necessary gas passage between tubes, for the products of combustion which heat the oil; and

Fig. 5 is a partial elevation of the tubes and spacers in Fig. 4 showing a method of holding them in place.

For example, in carrying out my invention for preparing kerosene, or, instead, fuel oil, if desired, for use in a fuel oil burner, I may proceed as follows:

In the accompanying drawings I have shown a fuel tank 1 which is preferably located below the level of the ground, the same being provided with a steam-heating coil 2 supplied with steam by a valved inlet pipe 3, a draw-off pipe and strap 4 being provided for conducting away the condensate from the steam. The heat from the steam is provided for the purpose of reducing the viscosity of the fuel, when necessary, so as to make it pump more easily. The kerosene is drawn ofi from the tank 1 by a pipe 5 by suction, said pipe 5 being connected with a triplex force pump 6 provided with tight and loose pulleys 7 and 8 for driving the same by any suitable source of power. The pump 6 puts the oil under pressure ranging from 200 to 400 lbs. per square inch gage. In the cases of coal tar distillates, or alcohols, much higher pressures will be required. The pump 6 delivers the oil under pressure through a pipe 9 having a hand-operated valve 10, and thence by a branched pipe 11 to a pair of headers 12 and 13 of a heater located in a heating and combustion chamber 14, which chamber is formed of refractory material and insulated substantially as shown, and is arranged so as to provide gas passages for the products of combustion through a series of heater tubes 16 and 17 connected to the headers 12 and 13, and a smokeboX 18 which discharges into a stack 19. The heater tubes serve to raise the incoming oil to the desired temperature. A sufliciently large set of tubes 16 and 17 is provided for a unit, for example 72 tubes, capable of handling 3000 lbs. of

.oil per hour, alternate tubes being arranged result if all the tubes were led into one header. The set of tubes 16 and 17 pass longitudinally through the chamber 14, said tubes having a series of vertical U-shaped turns 20 therein and finally terminating by being connected alternately to the two discharge headers 21 and 22. The whole series of tubes 16 and 17 are connected together by channels or buckstays 23 and 24 with spacing blocks 23a suitably formed to fit the contour of the tubes as shown, at such places as may be required in the design of the gas passages to secure the necessary velocity of gases over the tubes, the aforesaid blocks being held in place vertically by cross pieces 24a enga 'ng the blocks, said cross pieces being firmly eld in place, preferably by securely attaching them to the channels or buckstays- 23 and 24 located on both sides of the bank of tubes, which latter are drawn together by through bolts 25 and 26, pressing the tubes firmly against the blocks 23a, thereby forming a rigid heater unit. The bolts 25 and 26 extend through the channel members 23 and 24 at sufliciently frequent intervals to secure the desired rigidity, passing through the entire series or bank: of tubes. Furthermore, suitable bafiles incIuding two substantially horizontal baffles 27 and 28 and two vertical baffles 29 and 30, are arranged to give the most effective flow of hot gases or products of combustion through the series of tubes 16 and 17. It will be noted that the two headers 21 and 22 are connected togetherby a passageway 31 so that they may both have communication with a vapor-discharge pipe 32 provided with a hand-valve 33 and thence with a fitting 34 having a branch pipe 35 controlled by a hand-valve 36 adapted to bleed off some of the fuel to a discharge or burner nozzle 37 located inside of the tirebox end of the chamber 14 beyond the baifle 30. The furnace at this point has an opening .38 for air, which opening is partly filled by a preliminary heater 39 designed to be supplied with liquid oil from a valved pipe 40 for the initial heating or starting of the apparatus.

The vaporized oil continues up the pipe 32 to a header box 41 having a thermometer 42 therein and a gooseneck 43 leading to a pressure gage 44. The fuel expansion may be watched by means of these pressure and temperature devices, and regulated according to them, the header box 41 being provided for this purpose with a shut-off valve 45 leading to a pipe 46 which is adapted to supply oil to a plurality of burners adapted to heat any desired kind of power plant, as, for

example, a steam boiler 46a of any desired construction. Said header box 41 is also provided with a hand-valve 47 which controls the purging of the system of cool liquid and gas or air contained in the system and may be used as an overflow for the gaseous fuel until the pressure and temperature are suitable for use in the burners or other devices fed by the pipe 46, said overflow being carried through a pipe 48 into the tank 1. A breathcrpipe 48a on the tank 1 permits of the escape of any permanentgases and relieves any pressure generated by the heating of the tank contents. Where use of the purgmg line 48 may be required frequently, or where large amounts may be purged, the length of the pipe 48 may be increased, and arranged in any desired manner, thereby increasing the pipe surface available for acting as a condenser by condensing thefuel gases being returned to the tank. The sloping position of the pipe enables the pipe to drain in the direction of the tank 1.

In the operation of my process steam is supplled to the coil 2 in the tank 1, if necessary. The starting burner 39 is lighted and the pump 6 is also started after opening the valve 10. Oil, vapor and trapped gases will vent back to the tank 1 freely until the system is purged, thereupon the valve 47 will be partially closed, the pump 6 running slow ly so as to secure the proper pressure in the system as indicated by the pressure gage 44. As soon as the temperature reaches the desired magnitude, as indicated by the thermometer '42, the valve 36 may be opened gradually until the vapor at the burner 37 ignites, whereupon the burner 39 may be shut down by closing the valve 40. The valve 45 may now be opened slightly and the valve 47 closed, the ump 6 speeded up, and the valves 45 and 36 opened to the extent necessary to maintain the temperature while furnishing the desired amount of gaseous oil to the boiler burners or other devices to which the pipe 46 is connected. Further control of the apparatus is obtained from now on by speeding up or slowing down the pump 6, and varying the amount of oil reaching the burner 37 by controlling the valve 36, this being done so as to maintain the pressure registered by the pressure gage 44, and the temperature as registered by the thermometer 42 at the desired values. Also, if desired, suitable heat insulation material 49 may be provided in clothing the part located within the heat combustion chamber 14, or, in fact, around any of the other parts wherever desired, especially all pipes carrying hot gas under pressure. However, as a cooling effect in the pipe 48 is desired it woud be undesirable to clothe the same with heat insulating material. Also, if desired, a heat insulating layer 50 may be provided in the floor of the combustion chamber underneath the refractory lining, the whole being carried on a suitable foundation, as, for example, piers 51 and steel work 52, as shown, or direct on the ground or incombustible floor.

It will, of course, be obvious that the above described apparatus is only one form of the apparatus which may be used for carrying out the process contained in my invention, and the various parts and arrangement of parts, including methods of control, are capable of wide variation to meet the conditions under which the apparatus is to be used.

It is recognized by physicists that a substance existing above its critical temperature is, for that temperature or a higher one, a permanent gas. In view ,of the fact that I prefer to operate above the critical temperature of the fuel selected I have, in the foregoing description, referred to the fuel as gaseous or gasified. However, since my invention is not limited to actually passing the critical temperature, as a slightly lower temperature will give results approximating the preferred condition, and since the gasified fuel may drop below the critical temperature and become a vapor on expansion, I refer in the claims to gas-like vapor as covering the fuel in its condition at the point of use, irrespective of whether at that time it is technically a gas or a vapor.

While I have described my invention above in detail I wish it to be understood that many changes may be made therein without departing from the spirit of the same.

I claim:

1. The method of utilizing normally liquid fuels which comprises the steps of heating a liquid adapted to be used as a fuel to a temperature substantially at least as high as the critical temperature thereof while maintaining it at a pressure of the order of the critical pressure thereof, conveying directly while in this condition to the apparatus controlling the consumption of the same and oxidizing the fuel while in the form of a gaslike vapor.

2. The method of utilizing normally liquid fuels which comprises the steps of heating a liquid fuel to a temperature substantially at least as high as its critical temperature but below that at which substantial thermal decomposition takes place while mainresulting gas-like vapor to expand into a gas comprising free oxygen and burning th resulting mixture.

4. The method of utilizing normally liquid fuels comprising the steps of preatomizing by heating a liquid fuel to a temperature at least as high as the critical temperature while maintaining it at pressures sufliciently great to keep the density of approximately the order of that of a liquid, injecting into a free oxygen containing gas and burning the resulting mixture.

5. The method of utilizing a liquid fuel Which comprises the steps of heating a liquid fuel above the critical temperature thereof, while-maintaining at a pressure great enough to substantially prevent boiling, permitting a portion of the resulting gas-like vapor to expand, utilizing the energy in the gas to cause the same to mix with gases containing free oxygen and burning the same.

6. The method of utilizing a fuel which comprises the steps of heating a liquid adapted to be used as a fuel to a temperature sub stantially at least as high as the critical temperature thereof, while maintaining it at a pressure of the order of the critical pressure thereof and utilizing such fuel while in such condition for a reducing process.

7. The method of utilizing a fuel which comprises the steps of heating a liquid fuel to a temperature substantially at least as high as the critical temperature thereof, under a pressure substantially of the order of its critical pressure, conducting the resulting gas-like vapor to the point of combustion and adjusting the pressure at the point of generation of the gas-like vapor to control the combustion of the fuel.

8. The method of utilizing a liquid fuel which comprises the steps of heating a liquid fuel rapidly to a temperature at least as high as approximately the critical temperature thereof and suflicient to cause undesirable thermal decomposition of the fuel on long exposure, maintaining a pressure sufiicient to maintain the fuel substantially liquid while below the critical temperature, and immediately burning the fuel heated to such temperature, whereby undesirable thermal decomposition is substantially prevented.

In testimony that I claim the foregoing, I have hereunto set my hand this tenth day of Au ust, 1928.

ED ARI) ADAMS RICHARDSON. 

